WebHook has been created but never triggered

So I've just created a WebHook. When I retrieve a list of subscriptions the hook is in there and has status "Active". But when I send SMS it doesn't being triggered. My server access logs are empty.

What's the problem? .

public $uri =>

string(103) "https://platform.devtest.ringcentral.com/restapi/v1.0/subscription/364ca852-8404-48c0-a636-ad79c3d223ef"

public $id =>

string(36) "364ca852-8404-48c0-a636-ad79c3d223ef"

public $creationTime =>

string(24) "2021-03-17T09:07:36.549Z"

public $status =>

string(6) "Active"

public $eventFilters =>

array(1) {

[0] =>

string(82) "/restapi/v1.0/account/291360004/extension/291360004/message-store/instant?type=SMS"

}

public $expirationTime =>

string(24) "2031-03-15T09:07:36.549Z"

public $expiresIn =>

int(315358704)

public $deliveryMode =>

class stdClass#6711 (3) {

public $transportType =>

string(7) "WebHook"

public $encryption =>

bool(false)

public $address =>

string(56) "https://MY_DOMAIN/api/hooks/public/sms"

}